Maternal breast-milk and intestinal bifidobacteria guide the compositional development of the Bifidobacterium microbiota in infants at risk of allergic disease

Background The sources and the impact of maternal bacteria on the initial inoculum of the intestinal microflora of newborn infants remain elusive. Objective To assess the association between maternal breast‐milk and fecal bifidobacteria and infants' fecal bifidobacteria. Methods Sixty‐one mother–infant pairs were included, special emphasis being placed on the maternal allergic status. Bifidobacteria were analysed by a direct PCR method in fecal samples from mothers at 30–35 weeks of gestation and from infants at 1 month of age and from breast‐milk samples 1 month post‐partum. Results Fecal Bifidobacterium adolescentis and Bifidobacterium bifidum colonization frequencies and counts among mother–infant pairs correlated significantly (P=0.005 and 0.02 for frequencies, respectively, and P=0.002 and 0.01 for counts, respectively). Only infants of allergic, atopic mothers were colonized with B. adolescentis. Each of the breast‐milk samples contained bifidobacteria [median 1.4 × 10³ bacterial cells/mL; interquartile range (IQR) 48.7–3.8 × 10³]. Bifidobacterium longum was the most frequently detected species in breast‐milk. Allergic mothers had significantly lower amounts of bifidobacteria in breast‐milk compared with non‐allergic mothers [median 1.3 × 10³ bacterial cells/mL (IQR 22.4–3.0 × 10³) vs. 5.6 × 10³ bacterial cells/mL (1.8 × 10³–1.8 × 10⁴), respectively, (P=0.004)], and their infants had concurrently lower counts of bifidobacteria in feces [3.9 × 10⁸ bacterial cells/g (IQR 6.5 × 10⁶–1.5 × 10⁹) in infants of allergic mothers, vs. 2.5 × 10⁹ bacterial cells/g (6.5 × 10⁸–3.2 × 10¹⁰) in infants of non‐allergic mothers, P=0.013]. Conclusions Breast‐milk contains significant numbers of bifidobacteria and the maternal allergic status further deranges the counts of bifidobacteria in breast‐milk. Maternal fecal and breast‐milk bifidobacterial counts impacted on the infants' fecal Bifidobacterium levels. Breast‐milk bacteria should thus be considered an important source of bacteria in the establishment of infantile intestinal microbiota.